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Abstract

The performance of fiber-reinforced
composites is often controlled by the
properties of the fiber-matrix interface. Good
interfacial bonding (or adhesion), to ensure
load transfer from matrix to reinforcement, is a
primary requirement for effective use of
reinforcement properties. Thus, a fundamental
understanding of interfacial properties and a
quantitative characterization of interfacial
adhesion strength can help in evaluating the
mechanical behavior and capabilities of
composite materials. A large number of
analytical techniques have been developed for
understanding interfacial adhesion of glass fiber
reinforced polymers. Common adhesion tests
include contact angle measurements, tension or
compression of specially shaped blocks of
polymer containing a single fiber, the single
fiber pull-out test, single-fiber fragmentation
test, short beam shear and transverse tensile
tests, and the vibration damping test. Among
these techniques, the vibration damping
technique has the advantage of being
nondestructive as well as highly sensitive for
evaluating the interfacial region, and it can
allow the materials industry to rapidly
determine the mechanical properties of
composites. In this work, we contributed a
simple optical system for measuring the
damping factor of uniaxial
fiber-reinforced-polymer composites in the
shape of cantilever beams. A single glass fiber-
and three single metallic wire-reinforced epoxy
resin composites were tested with the optical
system. The fiber- (wire-) matrix interfacial
adhesion strength measurements were made by
microbond test. A reasonable agreement was
found between the measured interfacial
adhesion strength and micromechanics
calculations using results from vibration
damping experiments. The study was also
extended to multi-fiber composites. The
interfacial damping factors in glass-fiber
reinforced epoxy-resin composites were
correlated with transverse tensile strength,
which is a qualitative measurement of adhesion
at the fiber-matrix interface. Four different
composite systems were tested. For each
system, glass fibers with three different surface
treatments were used at three different volume
fractions. The experimental results also showed
an inverse relationship between damping
contributed by the interface and composite
transverse tensile strength for all of the
multi-fiber composites.